The best mattress for side and back sleepers is medium to medium-firm, around 5.5 to 6.5 out of 10, with a comfort layer of at least 2" that relieves pressure at the shoulders and hips and a firm support core that keeps the lower back from sagging. Side sleepers need a little more give at the surface. Back sleepers need a little more support underneath. A good medium-firm mattress covers both, which is why it suits most couples.
We designed both Cozey mattresses for side and back sleepers, so this is the question we spend the most time on. This guide explains what each position needs, how firmness should change with body weight, what to look for in a mattress's layers, and when a medium-firm mattress isn't the right call.
On This Page
- What Do Side Sleepers Need in a Mattress?
- What Do Back Sleepers Need in a Mattress?
- How Firm Should Your Mattress Be?
- What to Look For in a Mattress's Layers
- Pillows and Setup Tips
- Cozey Mattresses for Side and Back Sleepers
What Do Side Sleepers Need in a Mattress?
Summary: Enough softness at the surface for your shoulder and hip to sink in, and enough support underneath that your waist doesn't sag. When it's right, your spine forms a straight line from your neck to your hips.
On your side, your weight rests on two narrow points: the shoulder and the hip. On a mattress that's too firm, those points take all the pressure. That's what causes a numb arm, an achy shoulder in the morning, or tossing and turning to find relief. On a mattress that's too soft, your hips sink lower than your shoulders and your spine bends sideways through the night.
What works is a comfort layer that lets the shoulder and hip sink in a little, over a support layer firm enough to hold the waist up. That's why a medium to medium-firm mattress with a decent comfort layer suits most side sleepers better than a very firm one.
Signs your mattress isn't working for side sleeping
- Your bottom arm or shoulder goes numb or tingles
- You wake up with a sore shoulder or hip
- You change sides constantly through the night
- You can feel a dip where your hips rest
What the pressure data shows
Shoulder pressure is the clearest test for side sleepers. In pressure mapping by Carpenter Co., which makes the Serene® foam in our comfort layer, 2" foam samples were tested with a person lying on their side:
What the pressure data shows
| Comfort foam | Average shoulder pressure (mmHg) | Peak shoulder pressure (mmHg) |
|---|---|---|
| Serene® foam | 19.19 | 36.11 |
| Memory foam | 24.03 | 37.71 |
| Standard foam A | 24.46 | 40.42 |
| Standard foam B | 24.81 | 41.80 |
Lower is better. These are tests on foam samples rather than finished mattresses, but they show why the comfort material on top matters so much for side sleepers.
What Do Back Sleepers Need in a Mattress?
Summary: Firm, even support under the hips and lower back, with just enough give that the natural curve of your spine is filled in. Medium-firm is the sweet spot for most back sleepers.
On your back, your weight is spread over a larger area than on your side, but it isn't spread evenly. Your hips are the heaviest part and press deepest. On a mattress that's too soft, the hips sink and your spine sags like a hammock. On one that's too firm, there's a gap under the small of your back and pressure builds at the tailbone and shoulder blades.
The right mattress fills in the curve of your lower back while holding your hips level with your shoulders. That takes a supportive core with a comfort layer that's responsive rather than mushy.
Signs your mattress isn't working for back sleeping
- You wake up with a stiff lower back that eases once you're up
- You can slide your hand easily under your lower back when lying flat
- Your hips feel lower than your shoulders
- You keep rolling onto your side to get comfortable
What the pressure data shows
In Carpenter's back sleeping test, 2" foam samples were placed on a very firm surface to see how well each one spread the load on its own:
What the pressure data shows
| Comfort foam | Average pressure (mmHg) | Peak pressure (mmHg) |
|---|---|---|
| Serene® foam | 18.61 | 58.71 |
| Standard foam B | 20.33 | 72.52 |
| Standard foam A | 20.02 | 98.31 |
| Memory foam | 21.41 | 220.00 |
The memory foam sample let pressure build up sharply around the hips, while Serene kept the peak 73% lower. For back sleepers, that's the difference between support that feels even and a bed with one sore spot.
How Firm Should Your Mattress Be?
Summary: Most side and back sleepers do best between 5.5 and 6.5 out of 10. Lighter people usually need a little softer, heavier people a little firmer.
Firmness feels different depending on your weight. A lighter person barely sinks into a medium-firm mattress, so it feels firmer to them. A heavier person sinks further, so the same mattress feels softer. Use this as a starting point:
How Firm Should Your Mattress Be?
| Body weight | Side sleepers | Back sleepers | Combination sleepers |
|---|---|---|---|
| Under 130 lb | 4.5 to 5.5 | 5 to 6 | 5 to 6 |
| 130 to 230 lb | 5.5 to 6.5 | 6 to 7 | 5.5 to 6.5 |
| Over 230 lb | 6 to 7, with a thicker comfort layer | 6.5 to 7.5 | 6.5 to 7 |
Firmness scales aren't standardized, so treat these as ranges rather than exact targets. For reference, our Foam Mattress sits around 5.5 to 6 and our Hybrid around 6 to 6.5.
What if you share the bed?
If one of you sleeps on your side and the other on your back, medium-firm is usually the best compromise. It gives the side sleeper enough cushion and the back sleeper enough support. If your weights are very different, the lighter partner will find the bed firmer than the heavier one, so lean toward the softer end of the range.
What to Look For in a Mattress's Layers
Summary: A comfort layer of at least 2" that relieves pressure without trapping you, a transition layer, and a dense support core. The materials matter more than the marketing names.
What to Look For in a Mattress's Layers
| Layer | What side and back sleepers should look for | Why |
|---|---|---|
| Comfort layer | At least 2" of pressure-relieving foam or latex | Gives shoulders and hips somewhere to sink |
| Comfort material | Responsive, not heat sensitive | Memory foam can feel firmer in a cool room and make it harder to roll over |
| Transition layer | A slightly firmer foam, around 2" | Stops you from sinking straight through to the core |
| Support core | High-density foam or individually wrapped coils, about 6" | Keeps your hips level with your shoulders |
| Edge support | Firm edges, especially on a hybrid | Lets you use the full surface and sit on the side |
| Weight rating | Covers you and your partner individually | Support drops off above a mattress's rating |
Two things are worth watching out for. First, very thick, soft comfort layers feel great in a showroom but can let your hips sink over a full night, especially for back sleepers. Second, if you switch between your side and your back, look for a comfort material that responds quickly, so you're not fighting the mattress each time you turn.
Pillows and Setup Tips
Summary: The right mattress only does half the job. Your pillow and your bed base finish it.
For side sleepers
- Use a higher pillow. It should fill the gap between your shoulder and your ear, so your head stays level with your spine.
- Try a pillow between your knees. It keeps your top leg from pulling your hips out of line.
For back sleepers
- Use a medium-height pillow. Too high pushes your chin toward your chest. Too low lets your head tip back.
- Try a small pillow under your knees. It takes a bit of strain off the lower back.
For everyone
- Check your base. An old, sagging box spring or widely spaced slats will undo a good mattress. Slats should be no more than 3" apart, and Queen and King sizes need center support.
- Rotate the mattress. Turning it head to foot every 4 to 6 months spreads out wear where your hips and shoulders rest.
- Give it a few weeks. If you're coming from a soft or sagging mattress, a supportive one can feel firm at first. Most people adjust within a few weeks.
Cozey Mattresses for Side and Back Sleepers
Summary: Both Cozey mattresses were designed for side and back sleepers, with a 2" Serene® comfort layer over a firm core. Choose the Foam Mattress for a closer, stiller feel, or the Hybrid for more lift, airflow and edge support.
Cozey Mattresses for Side and Back Sleepers
| Cozey Foam Mattress | Cozey Hybrid Mattress | |
|---|---|---|
| Firmness | Medium-firm, 5.5 to 6 out of 10 | Medium-firm, 6 to 6.5 out of 10 |
| Comfort layer | 2" Serene® foam | 2" Serene® foam |
| Transition layer | 2" high-density foam | 2" high-density foam |
| Support core | 6" high-density foam | 6" pocket coils (1,200 in a Queen) with a foam edge rail |
| Best for | Side sleepers who like a hug, couples who wake easily | Back sleepers who like more lift, combination sleepers, hot sleepers |
| Queen price | $695 | $895 |
Both are made in Canada, rated for up to 250 lb per sleeper, and come with a 100-night trial and a 15-year limited warranty. During the trial, you can exchange one for the other.
If you mostly sleep on your side and want to feel cradled, start with the Foam Mattress. If you're mostly on your back, switch positions through the night, or sleep warm, start with the Hybrid. It's the one I sleep on.
When a Cozey mattress isn't the right pick
- You weigh more than 250 lb. A thicker or firmer mattress built for that load will support you better long term.
- You sleep mostly on your stomach and want a very firm bed. Medium-firm can let the hips dip for heavier stomach sleepers.
- You want a plush, sink-in feel. Both of our mattresses are medium-firm by design.